fiber has 171k rows, customers has 21k rows

haversine.rb

require 'csv'
require 'haversine'

fiber = CSV.read("fiber/all_florida_fiber.csv", {headers: true}).first(3)
customers = CSV.read("prospect_customers_geocoded.csv", {headers: true, encoding: 'ISO-8859-1'}).first(3)

hh = Hash.new { |hsh,key| hsh[key] = [] }

#for each customer, loop through all the fiber coords
customers.each do |customer|
  fiber.each do |fib|
    hh[customer["cid"]].push Haversine.distance(customer["Latitude"].to_f, customer["Longitude"].to_f, fib["lat"].to_f, fib["long"].to_f).to_feet.round(2)  
  end
end

vals = hh.map { |k, v| v.min } 

CSV.open("hash_output.csv", "wb") {|csv| vals.each {|elem| csv << [elem]} }